Wedge Driven Pipe Bending Machine

ABSTRACT

A pipe bending machine has a stiff-back which is driven by a pivoting wedge. A linkage applies force from the actuator to the wedge in a direction parallel to a longitudinal axis of the stiff-back. The stiff-back pivots on a first fulcrum and the wedge slides on a bed which pivots on a second fulcrum. The actuator drives the wedge between the stiff-back and the bed to rotate the stiff-back at the first fulcrum and bend the pipe seated in the stiff-back against the pipe bending face of a die. The conversion of the longitudinal force applied to the wedge into a transverse force applied to the stiff-back provides a significant mechanical advantage which varies directionally as the stiff-back rotates about its fulcrum to maintain a constant force on the stiff-back.

BACKGROUND OF THE INVENTION

This invention relates generally to pipe bending equipment and moreparticularly concerns machines used to bend steel pipe.

Known pipe bending machines level a pipe against a die with a pin-uplocated on one side of the die and apply force to the pipe on the otherside of the die with a stiff-back, typically powered by hydrauliccylinders, to bend the pipe against the die. The maximum bend typicallytotals 15-16° and the total is achieved by sequential pulls. In eachpull, the pipe is bent approximately ½°. Each pull results in a plasticdeformation of the pipe. The cylinders of known machines apply the forcedirectly to the stiff-back. Therefore, known machines generally requirelarge diameter cylinders capable of generating forces in a range of750,000 pounds. Typically, the cylinders required are in the range of9-14″ in diameter. Such a requirement imposes serious limitations oncapabilities of the machine.

First, the larger the diameter of the cylinder, the greater will be thelikelihood of leakage and other defects in cylinder operation. Second,the maximum industry standard cylinder is 8″ in diameter. Therefore,cylinders for this application are currently custom made, usually at twoto three times the cost of standard cylinders. Third, even though thecustom cylinders are very large, known machines still require the use oftandem cylinders tied together. In this configuration, changes incylinder orientation occur as the cylinders rotate in slightly differentradii. This results in the cylinders competing with each other, reducingthe net bending force available. In the worst such cases, thecounteracting cylinders may bind. Fourth, the resulting reduced cylinderdiameter to stroke ratio can cause the stiff-back to overshoot theintended bending angle of the pipe due to reduced controllability.

It is, therefore, an object of this invention to provide a pipe bendingmachine that will operate efficiently with standard size cylinders.Another object of this invention is to provide a pipe bending machine inwhich cylinders are not tied in a possibly competing configuration. Itis also an object of this invention to provide a pipe bending machinethat reduces the risks of overshooting intended bending angles.

SUMMARY OF THE INVENTION

In accordance with the invention, a pipe bending machine has astiff-back which is driven by a pivoting wedge to provide a significantmechanical advantage against the stiff-back as the stiff-back rotatesabout its fulcrum.

The pipe bending machine employs a die, a trough pivoted on a firstfulcrum, a bed pivoted on a second fulcrum, a wedge disposed between thetrough and the pivoted bed and an actuator driving the wedge between thetrough and the bed to bend a pipe seated in the trough against the die.Preferably, a linkage applies force from the actuator to the wedge in adirection parallel to a longitudinal axis of the trough.

Preferably, the die is fixed. The trough is pivoted on a first fulcrumabout a first axis parallel to a pipe bending face of the die andperpendicular to a longitudinal axis of the pipe. The bed is pivoted ona second fulcrum about a second axis parallel to the first axis. Thewedge is disposed between the trough and the pivoted bed. The actuatordrives the wedge between the trough and the bed to rotate the trough inrelation to the first fulcrum and bend the pipe seated in the troughagainst the pipe bending face of the die. The linkage applies force fromthe actuator to the wedge in a direction parallel to a longitudinal axisof the trough as the trough longitudinal axis rotates in relation to thefirst fulcrum.

Preferably, the pipe bending face is on a downstream portion of the dieas the pipe is longitudinally transferred through the machine. The firstfulcrum is downstream of the upstream portion of the pipe bending faceand facilitates rotation about the first axis and perpendicular to thelongitudinal axis of the pipe. The second fulcrum is downstream of thefirst fulcrum and facilitates rotation about a second axis parallel tosaid first axis.

According to the method for bending the pipe, the pipe is positioned inthe trough which extends longitudinally downstream of the die forapplication by the die of a first force to one side of the pipe. Asecond force is exerted in a direction parallel to a longitudinal axisof the portion of the pipe positioned in the trough. The second force isconverted into a third force applied to the longitudinal trough on theopposite side of the pipe than and downstream of the first force to bendthe pipe against the first force. The third force is maintained inperpendicular relationship to the longitudinal axis of the portion ofthe pipe positioned in the trough as the pipe is bending against thedie. If the pipe is to be bent in incremental steps, the pipe is thenrepositioned for application of the first force downstream of theprevious application of the first force and the previous steps arerepeated.

Preferably, the step of maintaining the third force perpendicular to thelongitudinal axis of the portion of the pipe positioned in the trough isaccomplished by the sub-steps of maintaining the second force parallelto the longitudinal axis of the portion of the pipe positioned in thetrough as the pipe is bending against the die and maintaining the thirdforce perpendicular to the second force.

Preferably, the pipe is fed longitudinally with respect to a fixed dieand a trough, the trough being pivoted on a fulcrum on an upstreamportion of the trough. Feeding of the pipe is stopped at a position inwhich a leading portion of the pipe is aligned with the trough on oneside and a trailing portion of the pipe is aligned with the die on anopposite side. The wedge is driven between the downstream portion of thetrough and the bed to pivot the trough about the fulcrum and bend thepipe against the die.

Preferably, the step of driving the wedge is accomplished by thesub-steps of exerting a force on the wedge in a direction parallel to alongitudinal axis of the portion of the pipe seated in the trough andmaintaining the exerted force in parallel relationship to thelongitudinal axis of the portion of the pipe seated in the trough as thepipe is bending against the die.

If the pipe is to be bent in incremental steps, the pipe is fed furtherin the downstream direction. The further feeding of the pipe is stoppedat a second position in which a leading portion of the pipe is alignedwith the trough on one side and a trailing portion of the pipe isaligned with the die on an opposite side. The wedge is driven betweenthe downstream portion of the trough and the bed to pivot the troughabout the fulcrum and bend the pipe against the die. The steps offeeding, stopping and driving at predetermined incremental positionsalong the pipe are sequentially repeated until the bend is completed.

A pipe bender in accordance with this invention reduces the requiredhydraulic force by a factor in a range of 4:1 in comparison to knownpipe bending machines. It reduces the forces exerted by the cylinder andthe opportunity for leaks and defects. It puts the cylinders in a linearnon-competing, non-binding configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings in which:

FIG. 1 is a free-body diagram of the operating components of thepivoting wedge pipe bending machine;

FIG. 2 is a left side elevation view of the pivoting wedge pipe bendingmachine with the stiff-back in a fully lowered condition;

FIG. 3 is a right side elevation view of the pivoting wedge pipe bendingmachine with the stiff-back in a fully lowered condition;

FIG. 4 is a front elevation view of the pivoting wedge pipe bendingmachine with the stiff-back in a fully lowered condition;

FIG. 5 is a rear elevation view of the pivoting wedge pipe bendingmachine with the stiff-back in a fully lowered condition;

FIG. 6 is a perspective view of the front, top and left sides of thepivoting wedge pipe bending machine with the stiff-back in a fullylowered condition;

FIG. 7 is a perspective view of the front, top and right sides of thepivoting wedge pipe bending machine with the stiff-back in a fullylowered condition;

FIG. 8 is a left side elevation view of the pivoting wedge pipe bendingmachine with the side plate removed and the stiff-back in a fullylowered condition;

FIG. 9 is a left side elevation view of the pivoting wedge pipe bendingmachine with the side plate removed and the stiff-back in a fully raisedcondition;

FIG. 10 is a perspective view of the pivoting wedge pipe bending machinewith the side plate and stiff-back removed and the wedge in a fullyretracted condition;

FIG. 11 is a perspective view of the pivoting wedge pipe bending machinewith the side plate and stiff-back removed and the wedge in a fullyextended condition;

FIG. 12 is a perspective view of the wedge assembly of the pivotingwedge pipe bending machine;

FIG. 13 is an enlarged view of the area 13 of FIG. 11;

FIG. 14 is a perspective assembly view of the pivot roller clampassembly of the pivoting wedge pipe bending machine; and

FIG. 15 is a perspective view of the rear, top and left sides of thepin-up clamp assembly of the pivoting wedge pipe bending machine.

While the invention will be described in connection with a preferredembodiment thereof, it will be understood that it is not intended tolimit the invention to that embodiment or to the details of theconstruction or the arrangement of parts illustrated in the accompanyingdrawings.

DETAILED DESCRIPTION

Turning first to FIG. 1, the pipe P is to be bent against a die D. Thepipe P will be advanced along its longitudinal axis L in a downstreamdirection in incremental steps past the die D. “Downstream direction” isrelative and describes the movement of the pipe P in relation to themachine M. In practice, the machine M moves upstream in relation to thepipe P which is stationary. The pipe P is initially advanced to aposition at which it can be rested in a trough T, commonly referred toas a stiff-back, which extends longitudinally downstream of the die D.The trough T is pivoted on a first axis A₁, as shown on the upstreamportion of the trough T below the die D but downstream of theanticipated contact point C of the pipe P with the die D. The downstreamend of the trough T is supported by a wedge W which is supported by andreciprocally slides on a bed B which is pivoted on a second axis A₂.When the pipe P is in the initial position, a wedge driving force F₁which is directionally variable in relation to a third axis A₃ isapplied at a fourth pivotal axis A₄ to the wedge W in a directionparallel to the longitudinal axis L of the pipe P and the trough T. Thisresults in a trough lifting force F₂ being exerted on the trough T in adirection perpendicular to the wedge driving force F₁ applied to thewedge W. The application of the lifting force F₂ to the free end of thetrough T bends the pipe P against the opposing force F₃ of the die D toconform the portion of the pipe P downstream of the contact point C tothe shape of die D. As the sliding of the wedge W between the bed B andthe trough T causes the trough to rotate about its pivotal axis A₁, thedirection of the longitudinal force F₁ changes. However, the bed B andthe wedge W pivot on their respective axes A₂ and A₄ to maintain theforce F₂ perpendicular to the longitudinal axis L of the pipe P andtrough T as the pipe P is bending against the die D. After being bent tothe desired contour in initial position, the pipe P will be advancedalong its longitudinal axis L in the downstream direction in incrementalsteps past the die D, repositioning the pipe P for application of thebending force F₂ downstream of the previous application of the bendingforce F₂. The steps are repeated until bending of the pipe P has beencompleted.

Turning now to FIGS. 2-7, a preferred embodiment of the machine 10 has achassis 11 mounted on a pair of idler tracks 13. One side plate 15, asshown on the left side of the machine 10, supports an operator platform17, a pneumatics platform 19 and inboard hydraulic cylinders 21 and 23.Another side plate 25, as shown on the right side of the machine 10,supports an hydraulics platform 27, a power system platform 29 andinboard hydraulic cylinders 31 and 33. Looking at the left side plate 15in FIGS. 2, 4, 5 and 6, a bender operation control box 35 is mounted onthe operator platform 17. An air tank 37 is mounted below and an aircompressor 39 is mounted on the pneumatics platform 19. Looking at theright side plate 25 in FIGS. 3, 4, 5 and 7, the engine 41 is mounted onand the fuel tank 43 is mounted under the power system platform 29. Theengine control box 45 is mounted on the operator platform 17 on the leftside plate 15. An hydraulic pump 47 is mounted behind the engine 41 andan hydraulic tank 49 is mounted on the hydraulic platform 27.

The interior components of the machine 10 mounted between the sideplates 15 and 25 are illustrated in FIGS. 4 and 5 and in FIGS. 8 and 9in which the left side plate 15 and its associated platforms andexterior components are removed, except for the inboard cylinders 21 and23. The inboard components include front and rear pipe receiving rollerassemblies 50 and 60, respectively, the stiff-back assembly 70, the dieassembly 80, the pin-up clamp assembly 90 and the wedge drive assembly100.

The front pipe receiving roller assembly 50 includes a forward extension51 of the chassis 11 with uprights 53 and 55 supporting a front roller57 on an axle 59. The rear pipe receiving assembly 60, best seen inFIGS. 10 and 11, includes uprights 63 and 65 from the chassis 11supporting a rear roller 67 on an axle 69.

The stiff-back assembly 70 includes the trough or stiff-back 71 which issupported proximate its rearward end by the inboard hydraulic cylinders21, 23, 31 and 33 which are pivotally connected on the stiff-back lugs73 and 75 (right side lugs 73 and 75 not shown), respectively, and tothe suspension shafts 77 and 79, respectively, extending through the dieassembly 80.

The die assembly 80, best seen in FIGS. 10 and 11, includes nestingplates 81 securing the die bars 83 in shape and position to bear againstthe pipe in the bending process. The pin up clamp assembly 90, best seenin FIG. 15, includes a short trough or clamp 91. A pin-up wedge 93 ispositioned between the clamp 91, which is guided by left and right arms95 (right side arm 95 not shown), and a slide 97. The wedge 93 isreciprocally driven by a pin-up hydraulic cylinder 99 pivotally mountedon the chassis 11 to raise and lower the clamp 91 between the guide arms95 toward and away from the die assembly 80.

The wedge drive assembly 100, best seen in FIGS. 8-11, includes a wedgeassembly 110, left and right outboard hydraulic driving cylinderassemblies 120, left and right stiff-back lift roller assemblies 130 andleft and right roller pivot clamp assemblies 140. The wedge assembly110, shown in greater detail in FIG. 12, includes a support plate 111connected along the hypotenuse edges of opposed side plates 113. Guides115, as shown with chamfered leading ends and extending on the outboardsides of the wedge assembly side plates 113 parallel to the supportplate 111, are provided to keep the wedge assembly 110 centered in thebender chassis 11 between the machine side plates 15 and 25. Holes 117are provided in the trailing ends of the wedge side plates 113 forconnecting the wedge assembly 110 to the driving cylinder assemblies120. Each of the driving cylinder assemblies 120 includes a drivingcylinder 121 pivotally mounted at its rearward end to the chassis 11 onan axle 123. The forward end of each driving cylinder 121 is pivotallyconnected to the wedge assembly 110 by a pin 125 through itscorresponding hole 117 in the wedge assembly 110. The leading end of thewedge assembly 110 slides reciprocally between the stiff-back liftroller assemblies 130 and the roller pivot clamp assemblies 140 inresponse to the extension and retraction of the driving cylinders 121,as best seen in FIGS. 8 and 9.

Continuing to look at FIGS. 8 and 9, each stiff-back lift rollerassembly 130 includes a platform 131 seated on the wedge assembly 110and supporting the forward portion of the stiff-back 71. Looking at FIG.14, channel guides 133 have rollers 135 forming tracks in the channelguides 133. Returning to FIGS. 8 and 9, one guide 133 on each side ofthe underside of the platform 131 receives the upper edges of the wedgeassembly side plates 113 onto the rollers 135. Turning to FIGS. 13 and14, each roller pivot clamp assembly 140 includes a platform 141 and achannel guide 143 with rollers 145 forming a track in the channel guide141. The channel guide 143 is mounted on top of its platform 141 andreceives the lower edges of the wedge assembly side plates 113 under therollers 145. A shaft 147 engaged in a bushing formed by upper and lowerclamp members 149 and 151, respectively, pivotally supports the rollerpivot clamp assembly 140 on the chassis 11.

The operation of the machine can best be understood in reference toFIGS. 8-11. FIGS. 8 and 10 show the stiff-back 71 in a fully loweredcondition in which the inboard hydraulic cylinders 21, 23, 31 and 33 arefully extended and the outboard hydraulic wedge driving cylinders 121are fully retracted. FIGS. 9 and 11 show the stiff-back 71 in a fullyraised condition in which the inboard hydraulic cylinders 21, 23, 31 and33 are fully retracted and the outboard hydraulic wedge drivingcylinders 121 are fully extended.

In operation, the bending process begins with the inboard hydrauliccylinders 21, 23, 31 and 33 fully extended and the outboard 121hydraulic cylinders fully retracted, as seen in FIG. 8. The pipe isgenerally, though not always, pushed into the machine 10 via its backend. A mandrel (not shown) aligned and sitting in the stiff-back 71 isinserted into the pipe to maintain the pipe circularity during bending.The air tank 37 and compressor 39 of the machine 10 are intended toserve a pneumatic mandrel used for this purpose. As The pipe is loadedinto the machine 10, it passes across the rear roller 67 and onto thefront roller 57 and eventually rests on the rollers 67 and 57 and abovethe stiff-back 71. As the pipe is loaded, it is marked to identify thepoints along the pipe at which “pulls” will be sequentially made, itgenerally taking multiple “pulls” to achieve a full bend.

Once the marked pipe is positioned for the first bend, the inboardhydraulic cylinders 21, 23, 31 and 33 are operated to retract lightlyuntil the stiff-back 71 raises the pipe into contact with the die bars83. The die bars 83 arc across their length so that the pipesubstantially makes linear contact across the width of the die assembly80. When contact is made, retraction is terminated with contact beingmaintained. The pin-up hydraulic cylinder 99 is then actuated to drivethe pin-up wedge 93 between the guide arms 95 and raise the clamp 91toward the die assembly 80 to pin the pipe against the die bars 83 alongthe linear contact line. The pin-up hydraulic cylinder 99 is de-actuatedwith the pipe in the pinned-up condition.

The outboard hydraulic driving cylinders 121 are then actuated to drivethe wedge assembly 110 forwardly between the rollers 135 of thestiff-back lift roller assemblies 130 and the rollers 145 of the pivotclamp assemblies 140. The stiff-back lift roller assemblies 130,including its platform 131, are raised as the wedge assembly 110 isdriven against the pivoted platforms 141 of the pivot clamp assemblies140, thus raising the stiff-back 71 about the stiff-back pivot lugs 73and 75 and the suspension shafts 77 and 79 to bend the pipe against thedie bars 83. Pivoting the inboard cylinders 21, 23, 31 and 33 on thesuspension shafts 77 and 79 allows inboard cylinders 21, 23, 31 and 33to operate without competing against each other. Pivoting the stiff-back71 on the lugs 73 and 75 allows the stiff-back to assume the orientationnecessary to conform to the orientation of the pipe. Since thestiff-back 71 is parallel to the roller assembly platform 131 supportingit, the driving force of the extending outboard hydraulic drivingcylinders 121 is applied to the wedge assembly 110 in a directionparallel to the stiff-back 71 and the pipe. Since the platforms 141supporting the wedge assembly 110 are pivoted, the driving force remainsparallel to the stiff-back 71 even though the stiff-back 71 is rotatingabout the lugs 75. Thus, the lifting force applied by the wedge assembly110 to the stiff-back 71 remains perpendicular to the direction of thedriving force of the outboard cylinders 121 and remains constant eventhough the alignment of the pivoting outboard cylinders 121 varies asthe pipe is bending against the die bars 83.

After the first bend is completed, the pin-up cylinder 99 is actuated towithdraw the pin-up wedge 93 and return the pin-up clamp 91 to itslowest position, the outboard cylinders 121 are fully retracted and theinboard cylinders 21, 23, 31 and 33 are fully extended to lower thestiff-back 71 and return the pipe to the front and rear rollers 57 and67. The pipe will then be advanced to the next mark and the precedingsteps repeated until bending of the pipe at all of the marks has beencompleted.

A pipe bending machine according to the present invention will typicallyafford a mechanical advantage in a range of 4:1 in comparison to knownpipe bending machines. This mechanical advantage reduces the forcesexerted by the driving cylinders 121. In some applications, mechanicaladvantages in a range of 6:1 are possible, depending on the coefficientof friction of the rollers 135 and 145 and the geometry of the wedgeassembly 110. The opportunity for leaks and defects is decreased, thecylinders 121 operate in a linear non-competing, non-bindingconfiguration and the cylinders 121 are reduced to standard commerciallyavailable sizes.

Thus it is apparent that there has been provided, in accordance withinvention, a pipe bending machine that fully satisfies the objects, aimsand advantages set forth above. While the invention has been describedin conjunction with a specific embodiment thereof, it is evident thatmany alternatives modifications and variations will be apparent to thoseskilled in the art in light of the foregoing description. Accordingly,it is intended to embrace all such alternatives, modifications andvariations as fall within the spirit of the appended claims.

What is claimed is: 1-6. (canceled)
 7. A method for bending pipecomprising the steps of: positioning the pipe in a trough extendinglongitudinally downstream of a die for application by the die of a firstforce to one side of the pipe; exerting a second force in a directionparallel to a longitudinal axis of the portion of the pipe positioned inthe trough; converting the second force into a third force applied tothe longitudinal trough the pipe on an opposite side of the pipe thanand downstream of the first force to bend the pipe against the firstforce; and maintaining the third force perpendicular to the longitudinalaxis of the portion of the pipe positioned in the trough as the pipe isbending against the die.
 8. A method according to claim 7 furthercomprising the steps of: repositioning the pipe for application of thefirst force downstream of the previous application of the first force;and repeating the previous steps.
 9. A method according to claim 7, saidstep of maintaining the third force perpendicular to the longitudinalaxis of the portion of the pipe positioned in the trough comprising thesub-steps of: maintaining the second force parallel to the longitudinalaxis of the portion of the pipe positioned in the trough as the pipe isbending against the die; and maintaining the third force perpendicularto the second force. 10-13. (canceled)